1. Field of the Invention
The present invention relates to a high pressure mercury lamp and a sealing member for the lamp.
2. Related Art Statement
A high pressure mercury lamp has been used in an OHP (overhead projector), a liquid crystal projector and a headlamp for a vehicle. Such lamp has a light-emitting vessel made of quartz and mercury vapor sealed in the vessel at a high pressure. The light-emitting vessel is made of quartz and thus transparent, so that discharge arc in the vessel emitting light functions as a point light source.
Japanese patent publication 55-117, 859 discloses a high pressure discharge lamp having a metal foil fixed in the end portion of the light-emitting vessel of quartz so that the end portion is pinch sealed. The metal foil may be composed of a molybdenum foil coated with the other metal such as tantalum, niobium, chromium, yttrium or the like. According to the sealing process, after the molybdenum foil is provided inside of the end portion of the vessel, the end portion is heated to soften it. After the end portion is softened, the molybdenum foil is pressed so that the end portion is sealed with a pressure applied from the end portion onto the foil.